Abstract: Engine ignition-timing is a basic combustion control feedback parameter, and is important for developing the homogeneous charge compression ignition (HCCI) combustion conditions. An ignition-timing identify method was proposed based on measuring vibration velocities and accelerations of the cylinder head using an engine block cylinder head’s finite element model and a vibration transmission system model. The vibration velocities and accelerations were measured on a 295 HCCI engine. The results show that there is a lag angle between the ignition timings determined by the vibration responses and determined by the rate of pressure rise and the second derivative of in-cylinder pressure in different conditions with the lag angle average value within system deviation. Therefore, the method based on vibration responses can be used to identify combustion timings.

Key words: homogenous charge compression ignition (HCCI), cylinder head vibration velocity, cylinder head vibration ?acceleration, ignition timing